问如何修改ui.bootstrap.dropdown以响应鼠标悬停在拖放按钮上？

EN

.directive('dropdownToggle', function () {
    return {
        require: '?^dropdown',
        link: function (scope, element, attrs, dropdownCtrl) {
            if (!dropdownCtrl) {
                return;
            }

            dropdownCtrl.toggleElement = element;

            var toggleDropdown = function (event) {
                event.preventDefault();

                if (!element.hasClass('disabled') && !attrs.disabled) {
                    scope.$apply(function () {
                        dropdownCtrl.toggle();
                    });
                }
            };

            element.bind('click', toggleDropdown);

            // WAI-ARIA
            element.attr({ 'aria-haspopup': true, 'aria-expanded': false });
            scope.$watch(dropdownCtrl.isOpen, function (isOpen) {
                element.attr('aria-expanded', !!isOpen);
            });

            scope.$on('$destroy', function () {
                element.unbind('click', toggleDropdown);
            });
        }
    };